class Person:
    height = None
    Weight = None

    def sing(self):
        print("sing")


class Student(Person):
    learn = None

    def __init__(self):
        super().height = 1
        super().Weight = 2
        self.learn = 3

    def study(self):
        print("studying")


class Employee(Person):
    practice = None

    def doing(self):
        print("doing")


if __name__ == "__main__":
    person = Person()
    person.sing()
    student = Student()
    student.sing()
    student.study()
    emp = Employee()
    emp.sing()
    emp.doing()
